1. Field of Invention
The present invention relates to a slurry composition for use in chemical-mechanical polishing applications and a method of using the slurry composition.
2. Description of Related Art
A variety of slurry compositions are known in the art for use in chemical-mechanical polishing glass and glass ceramic substrates. Such prior art slurry compositions generally consist of abrasive particles dispersed in deionized water and/or other liquids. Commonly utilized abrasive particles include, for example, cerium oxide, aluminum oxide, zirconium oxide, tin oxide, silicon dioxide and titanium oxide. Cerium oxide (CeO2) is most commonly used because it produces a relatively high removal rate when used to polish glass and glass ceramics.
One of the drawbacks with the use of cerium oxide abrasives is that slurry compositions containing cerium oxide (D=7.65 g/cm3) tend to hard settle. Hard settling describes the condition when the abrasive particles fall out the dispersion and accumulate to form a non-redispersible layer of sludge in the container or process equipment holding the slurry composition. Hard settling can result in clogged piping and other process equipment, which is highly problematic in an industrial operation.
Homola, U.S. Pat. No. 6,221,119, discloses a method of polishing glass and glass-ceramic substrates using a slurry containing cerium oxide and sodium polyacrylate. Homola teaches that adding sodium polyacrylate to an aqueous cerium oxide slurry composition tends to increase the polishing rate. However, addition of sodium polyacrylate does not improve, and in most instances, exacerbates the hard-settling condition when the slurry composition is recirculated during the polishing operation.